Ammonium requirement for radiation-induced accumulation of polyamines in suspension-cultured grape cells

The effects of radiation-mediated free radical production on polyamine metabolism were investigated in grape cells ( Vitis vinifera L. cv. Gamay) using a cell suspension culture. Putrescine (Put) synthesis was triggered in irradiated cells (0. 5 kGy) only when ammonium was present in the culture medium. Under these conditions. Put accumulated to a continuously high level. As also described for other kinds of stress, the level of spermidine was slightly enhanced and that of spermine unchanged. The role of ammonium was assessed by studying non-irradiated cell cultures. In the presence of ammonium, a transient increase of both arginine decarboxylase (ADC) activity and of Put synthesis was observed during the lag phase of growth. This Put enhancement was inhibited by difluoromethyl arginine and not by difluoromethyl ornithine, showing that increased Put synthesis occurs via the ADC pathway. When ammonium was withheld from the culture medium. ADC activity was still triggered though transient Put accumulation was completely suppressed. These results emphasize the importance of ammonium availability in cultured cells as a limiting factor for Put production. Polyamine synthesis, therefore, cannot be stimulated by gamma irradiation in the absence of an ammonium supply. These results support the hypothesis that Put synthesis is a detoxification process of the ammonium produced as a result of nitrogen recycling within stressed plant cells.     

Infection of Vitis vinifera (cv Chardonnay) Inflorescences by Colletotrichum acutatum and Greeneria uvicola

Detached Vitis vinifera (cv Chardonnay) inflorescences were inoculated with spore suspensions of either Colletotrichum acutatum or Greeneria uvicola at 25°C, and a combination of light microscopy, scanning electron microscopy and plating out of inoculated flowers on to dichloran rose bengal chloramphenicol agar was used to investigate the time frame for infection. Colletotrichum acutatum infection commenced within 2 h of inoculation, while infection by G. uvicola commenced between 12 and 18 h postinoculation. All parts of the flowers were infected by both fungi.     

Accumulation of tocopherols and tocotrienols during seed development of grape (Vitis vinifera L. cv. Albert Lavallée)

Tocopherols and tocotrienols are present in mature seeds. Yet, little is known about the physiological role and the metabolism of these compounds during seed development. Here we present data on tocopherol and tocotrienol accumulation during seed development in Vitis vinifera L. cv. Albert Lavallée (Royal). This species was chosen for its ability to synthesize both tocopherols and tocotrienols. It is shown here for the first time that during seed development there are significant differences in localization and accumulation kinetics of tocopherols and tocotrienols. Tocopherols are found homogeneously dispersed throughout all tissues of the seed, in concentrations ranging from 20 to 100 microg tocopherol per g dry weight. Tocopherol levels decrease gradually during seed development. In contrast, tocotrienols are only found in the endosperm of the seeds, accumulating in a sigmoid fashion during the maturation period of seed development. Tocotrienol levels were found to be (54+/-7.4) microg/g dry seed in 90-day-old seeds of V. vinifera L. Furthermore, tocotrienol biosynthesis is demonstrated in these seeds during tocotrienol accumulation and in an endosperm fraction isolated at 75 days after flowering.     

Phaeoacremonium spp. and Botryosphaeriaceae spp. Associated with Date Palm (Phoenix dactylifera L.) Decline in Iran

During spring and summer of 2011, a survey was undertaken on some palm groves in the Kerman province (south‐eastern Iran) to determine the fungal pathogens associated with date palm (Phoenix dactylifera L.) decline diseases. Samples were taken from date palm trees showing yellowing, wilting and dieback symptoms. Isolations were made from symptomatic tissues on malt extract agar (MEA) supplemented with 100 mg/l streptomycin sulphate (MEAS). Two species of Phaeoacremonium, Phaeoacremonium aleophilum and Pm. parasiticum, and two species of Botryosphaeriaceae, Botryosphaeria dothidea andDiplodia mutila, were isolated from affected trees and identified on the basis of morphological, cultural and molecular characteristics. Pathogenicity tests were performed on date palm (4‐year‐old potted plants) under greenhouse conditions. Based on the pathogenicity tests, Pm. aleophilum was the most virulent and caused the longest lesions. This is the first report of Pm. aleophilum and B. dothidea and their pathogenicity on date palm tree.     

RAPD marker in grapevine (Vitis spp.) similar to plant retrotransposons

When assaying for sequence heterogeneity within monomorphic RAPD-PCR products in grapevines (Vitis spp.), we observed partial digestibility of a marker with the restriction enzyme MspI. The degree of digestion varied reproducibly between different cultivars. To study this phenomenon, two of the amplification products were cloned and sequenced. They show 91.7% similarity to each other. The DNA analysed was found to possess high similarity to retrotransposons from higher plants. This element seems repetitive and dispersed throughout the genome. To our knowledge, this is the first report of retrotransposon-like elements in woody plants. Received: 15 August 1996 / Revision received: 7 October 1996 / Accepted: 20 October 1996     

Alnus glutinosa and Orientus ishidae (Matsumura, 1902) share phytoplasma genotypes linked to the ‘Flavescence dorée’ epidemics

Flavescence dorée (FD) is a grapevine disease caused by associated phytoplasmas (FDp) which are epidemically spread by their main vector Scaphoideus titanus. The possible roles of alternative and secondary FDp plant hosts and vectors have gained interest in terms of better understanding of the FDp ecology and epidemiology. The findings of a survey conducted in the surroundings of three vineyards in the southern Swiss Alps aimed at studying the possible epidemiological role of the FDp secondary vector Orientus ishidae and the FDp host plant Alnus glutinosa are reported. This work demonstrates that O. ishidae is able to complete its biological cycle on A. glutinosa and to acquire FDp and 16SrV phytoplasmas very efficiently with an infection rate of 69% for the nymphal instars and 85% for the imagoes. A high prevalence of the map genotype M50 (map type FD1), which is included in the S. titanus—grapevine epidemiological cycle, was found in O. ishidae and A. glutinosa. Additionally, M12 (map type FD3), M44 and M47 were also sporadically detected. Surprisingly, the grapevines tested during this work were all infected by M54 (map type FD2) only, while the few S. titanus caught in the vineyard canopy were all FDp free. In conclusion, the occurrence of infected common alder stands and O. ishidae nearby vineyards do not seem to play a prominent role in FD epidemics in southern Switzerland. Nevertheless, wild vegetation acts as a reservoir of the FDp inoculum, which may locally trigger a FD emergence if S. titanus populations are established inside vineyards.